It would be helpful if you mention the games that are already in this list. Also, are all the players trying to speedrun the game or playing blind? Do cutscenes get skipped? Do the other players see what happened in the game before they started playing?

A Girl Who Chants Love At the Bound of This World YU-NO took me 80 real world hours to figure out how to get the true ending (branching story, requires specific item usage at specific points in the story), but depending on the platform and intended audience it is not a game I would recommend for streaming. Although the latest remake censors the nudity, its still sexually explicit, and it contains some content I understand is from a different time and culture but I personally find replusive. Beside that stuff the story was fantastic, though. Plus, as a graphic adventure game, it’s probably not ideal.

But, if Graphic Adventure games aren’t a problem but sexually explicit ones are, Snatcher on the SEGA CD and Policenauts on the SEGA Saturn are both quite lengthy, and lacking in the explicit department. Although Policenauts has a cool fature where loading a game save gives you a summary screen of everything that has happened up to that point, Snatcher does not.

Metal Gear Solid might be a pretty good one, as I remember the game being quite long, cutscenes included.

The Legend of Zelda Twilight Princess could be a good pick as well.

Danganronpa games can be pretty long as well, and are interesting to people who like solving mysteries.

Shenmue could be a good pick because of its QTE sections, which are pretty fast and easy to lose. And everyone loves to see a streamer lose.

Silent Hill or Yakuza series might offer something more interesting.

XCOM 2 can be incredibly punishing to lose, and the game makes it pretty easy to lose.